FDL-5 MA & DC-X

These are the first pictures of the first ever kit release of the
Lockheed FDL-5 MA (manned) reusable spacecraft which I have good reason to
believe was tested between 1968 and 1973.

Lockeed FDL-5 MA model kit prototype, front view,with fuel tanks.
The photo can be advantageously compaired to the picture in the Bill
Sweetman book. The model is now 95% accurate, only small details will be
added, such as small "eyebrows" over the windows area, the windows
themselves, sharper fuel tanks nose cones, and slightly modified slope at
the back of the spacecraft.

Another view, showing the clean lines.

Another view, somewhat more from the top.

Another view, with the fuel tanks.

Top view, without fuel tanks.

Left side, size comparison with the X-38 kit in 1/48th, and FDL-5
to smaller scale.

The DC-X project, as it is right now. The newly redesigned
fuselage have been hollowed out. Size comparison with the L-301 kit, at the
same scale. I will have several much more spectacular pictures of both the
L-301, and several other prototypes to show you soon (I hope!), either on my
site or on the forum), from the same photo session (I am keeping the
surprise!).

This is the closest angle it gets to the picture in the Bill
Sweetman book. You can then compare the shape and see how close it matches.
I could not take the exact same angle, as it would have required bellows,
but, this one is pretty close.

What I learned about FDL-5 MA, and how I designed this unique new model kit:

The Lockheed FDL-5 MA Reusable Spacecraft (lifting body) is a manned vehicle that was developed by Lockheed, for the US Air Force, from the basic AF-FDL labs FDL-5 shape studies. The vehicle is part of the FDL-5, FDL-6, FDL-7, F-5, and HLD-35 family of high lift-to-drag-ratio of hypersonic shapes developed by the AF-FDL labs in the mid-1960's.
Between 1969 and 1973, Lockheed Missile and Space built a "full scale mock-up" of the vehicle.

It is highly likely that the "mock-up" was in fact the real vehicle, and that it was almost certainly flown (or at least built, and cancelled, like its predecessor, the X-20 Dyna-Soar). Which would explain why it is still classified 34 years later.

The FDL-5 used a special stabilization technique called "compression-sharing", using a specially contoured rear fuselage, which allowed it to use only a small, single vertical stabilizer, instead of the usual twin wing tip fins used by other hypersonic vehicles (this also have some RCS reduction advantages). The spacecraft used flip-out variable geometry wings for landing, as the FDL-5 shape was inherently unstable below Mach 1.5.

FDL-5 MA also possessed broader wings than the various FDL-7 configurations, as FDL-5 MA, unlike the FDL-7s did not have permanent short stub wings on its rear fuselage, and as such, had less lift surface available for low speed handling, during the last critical phase of it's flight following atmosphere reentry, for landing, this, the broader wings of FDL-5 MA.

The FDL-5 MA also used a reusable rocket engine, developed for a USAF project, and predecessor to the SSME: the XLR-129-P1. The same engine can be found on the Triamese proposals of General Dynamics.

Space crews also appear to have been selected, as mentionned in a technical paper,
(same case as what happened with the X-20, which information about spacecrews is now declassified and can be found on the web, pictures of crews included)(i am refering to the X-20 crews here, of course).

And i've got a bit of news for you: the engine used Fluorinated Hydrogen as fuel !! Definitely giving a higher Isp and high performance package, allowing FDL-5 MA to easily reach orbit(more details on this and metallic powders slurry inside the kit). Methyl hydrazine was used for the RCS and OMS engines.

Reusability of existing hardware was also studied, saving cost, in typical Lockheed fashion.
FDL-5 MA studies also included storable rocket propellants, and called for.. a storable spacecraft (!) (that seems to indicate a "silver bullet " capacity here, with the spacecraft remaining in storage for prolonged periods of time or years, ready to be used at a short moment's notice, for high priority reconnaissance or strike missions).
It's fuel tanks are double the diameter of the fuel tanks for the X-15 (and about double the lenght). So, that gives at least 8 times the internal volume of the X-15 A-2 fuel tanks (!!) (enough for orbital flight when launched from under the wings of a B-52).

The fuselage of FDL-5 MA have much more internal space for fuel than the X-15. The vehicle is a massive lifting body, and i found out it also longer than the X-15.

The external drop tanks feature "rings" that can be used to lift the tanks and install them prior to each flight (with a crane of specialized servicing vehicle).

Compression sharing (Horten sailsplane, X-20 stabilization ramp):

These 2 vehicles share very interesting stabilization characteristics with FDL-5. The Horten sailplane was a tailess design, using only a special wing whose incidence varies from the root to the wing tip. Although there was a small underfuselage "fin", it was used more as a landing gear integrated fairing than for directional stability per say, although i am sure it contributed to it also. Similarly, the FDL-5 uses a small vertical fin, but without sufficient surface to provide all the directional stability needed.

The FDL-5 flip-out wings deployed only at the very last moment, just before landing. That is because the landing gear was stowed above the retracted wings ! And the only way to deploy it (the landing gear) was to open the wings first (!).
A lot of the information about the shape of FDL-5 MA i learned simply by building the kit. It is surprising the amount of information one can learn from a couple of front view photos, a shadow on the ground, (and another very important element, which will be explained only with the kit historic and instructions), as well as the size of standard lettering, and other aircraft info.

I learned from the shape while building it, first starting with a pre-master, which i made from clay, and which i shaped until it roughly matched views of the 2 publicly known photos of FDL-5 MA. Then a fiberglass mould was made, and the clay model was sacrificed. Gelcoat and fiberglass was then laid into the mould, and became the new master. After considerable work, filling and careful reshaping, always in comparison to the 2 photos, the model became the final master for the FDL-5 MA model kit and now precisely match the photos. Having had the 2 photos showing 2 different angles (plus the dimensions i found from studying ( ), was a bit akin to having a stereoscopic vision of the spacecraft. Once the 3 dimensional model was built, it was only a matter of correcting until the shape matched the photos.

I can guarantee that the length and span I found for FDL-5 MA are accurate, to plus or minus a few inches, as the information I found is confirmed and cross-referenced from the lengths of 2 other very well known aircraft, from which dimensions are known. One of which was equivalent to the value of 1, while the FDL-5 MA was 2.5 times longer than it was. A third aircraft, the SR-71, only confirmed the dimensions I had already calculated for it, and showed the data to be very accurate (which was a big relief, it is always nice to see one's calculations confirmed a third time, if only for safety's sake). That info will be available inside the kit.

FDL-5 MA also possessed much broader wings than those used on the various FDL-7 configurations (this was confirmed by another Lockheed manned version of FDL-5 : MRS, and this makes sense: FDL-5 does not have have the FDL-7's permanent short stub wings on its rear fuselage, and as such, had much less lift generating surface available for low speed handling, during the last critical phase of its flight, following atmsphere reentry, just before landing, and it makes sense to compensate for that lack on the FDL-5 MA, by adding broader pop out wings. Thus, I adopted those for my model.
The FDL-5 MA would use jettisonable windshield fairings (like X-20) (not retractable fairings, unlike what was said in the Bill Sweetman book on Aurora), to protect its un-aerodynamic flat windows from melting during ascent and on reentry.

The flaps of FDL-5 manned MRS are hidden under the fuselage ! (like on X-38).

The X-15 A-2 external fuel tanks were designed for an acceleration to Mach 2 (Airpower, May 1978).

The FDL-5 MA fuel tanks have a nose cone sweep angle designed for acceleration up to Mach 3.

The flaps (elevons) are lodged under the fuselage (unlike FDL-5 A unmanned, where they are protruding completely outside the rear fuselage).

When one studies the 2 known photos of the aircraft, one can see no shawdows indicating any protruding flaps for the FDL-5 MA.

The shadows on the ground show that the trailing edge is not entirely straight. It does have a slight truncated V shape (reverse swept).

No rocket nozzle is seen protruding from the rear. (Unlike the manned Rockwell FDL-5 version. Which means the nozzle is embedded in the fuselage of the Lockheed "mock-up", and this makes sense too (protecting it from reentry heat).

Construction: (FDL-5 A) Upper Surface:

Hot carrying load structure:

Single corrugated Haynes 25/ Inconel 625

Modular heat shield

Dyna-Quartz internal insulation

In-direct active cooling

Hot load carrying structure:

Haynes 25 honeycomb sandwich

Inconel 625 S.C.

Dyna-Quartz internal insulation

Insulated and actively cooled structure:

Aluminum 2219T81 load carrying structure

Dyna-Quartz internal/external insulation

In-direct cooling

H.C. sand-post supported H.S.

Hot load carrying structure:

Single corrugated Haynes 25/ Inconel

Modular heatshield

Dyna-Quartz internal insulation

Lower Surface:

Insulated:

Fused silica

External insulation

Phenolic overlay

Dyna-Quartz

Internal-external insulation

Honeycomb sandwich post supported heat shield (Columbium 752 R512)

Hot load carrying:

Dyna-Quartz

Internal insulation

In-direct active cooling

Insulated and actively cooled:

Dyna-Quartz

Internal-external insulation

honeycomb sandwich post supported heat shield (Cb 752 R512)

The structure assembly was made of an external metallic heat shield (single corrugated panels), with internal insulation immediately inside, toped by coolant tubes (circulating inside double corrugated structural panels), onto which was attached the internal frame. So we have 4 elements.

Other materials include Titanium (longerons), and Tantalum (nose section). The hot fin structure was made of Haynes 25.
It is interesting to note that a photo of a corrugated metal hot structure heat shield for either an FDL-7 or the FDL-5 A vehicle was shown in an old issue of Lockheed Horizons, and correspond exactly to the shape needed for side panels for the rear fuselage of either of those vehicles.

Front landing gear:
In the context of the late 60's the choice of a metal wheels front gear indicate the difficulties encountered in protecting inflated rubber tires in a metal heat sink airframe, with technology available in the late 60's.

Skids were used for the main landing gear and metal wheels for the front gear.
This must have made for a rough landing, and for a choice of landing sites on dry lakes only, such as Edwards, Groom Lake, Tonopah, etc.

Ejection seats: of Gemini !
this would be the only logical choice, because of the special balute ejection system, unique to Gemini, that permitted for ejection from space (!!) (and reentry), for an astronaut wearing a standard full pressure suit. It was the only one that had such a capacity built-in.

This is also the only part of the kit, along with the internal shape of the cockpit interior (loosely based on that of Gemini, or the F-111) where I used an educated guess.

X-15 ejection seat: to Mach 4 only
X-20 seat: 70 knots to Mach 0.9 only... (below Mach 1)
SR-71 seat: to Mach 3 only.
X-20 being a pure sailplane and not having any onboard engine with the risks associated with fuels and oxydizers and such, could do away with a specialized ejection seat, as the only risks to the pilot would have been during landing. Thus that eliminated that seat.
SR-71's seat did not cover the whole flight envelope of FDL-5. Same with the X-15 seat, although it would have been a decent alternative, and was considered for a Rockwell proposal for an hypersonic (albeit, non-orbital) proposal, rival to the X-24C.

With the cockpit at the rear, the front landing gear taking some space, and the wings and skids taking yet more space behind the canopy, that left not much space for a cargo bay... All the frontal space would have been used for the one large hydrogen fuel tank, plus the smaller nitrogen pressurization tanks in the nose, and black boxes. Immediately behind the cockpit wall and the 2 pilots, the space would taken by the 2 oxygen oxydizer tanks, one on each side of the engine. The FDL-5 MA appeared to have no docking mechanism or sas, seriously restricting its mission. This indicates the program would have not been used in conjunction with a military space station nor to service it.

The mission was probably to carry one small projectile (tightly fitted)(either kinetic, or nuclear)(or like in the case of the X-20, a small carbine, coupled with a radar, or small rockets, to destroy satellites).
Because of the tight package, this would have left minimal space to carry a reconnaissance camera. Though such equipment can be made to fit in a tight package (like in the case of the D-21). The only space available would have been behind the cockpit, just in front of the fin, a fused quartz window could have been installed there, as view port for the folded optics camera.
Thus, missions would have had to be alternated. Different internal configuration and mission package for each specific mission (camera bay, or weapon's bay); (or some external payload fairing, but at a cost of weight penalty. This could also have been fitted as integral part of the external drop tanks, but this would have caused a problem.. as the drop tanks had to be jettisonned at Mach 3. Thus that solution would not have allowed to bring to orbit some extra external payload for strike. Suborbital strike would still have been possible, if a B-52 carrier could have approached sufficiently close a target's border without being detected.. but that is unlikely. This would also have wasted a very costly FDL-5 MA asset and crew).

The correct Lockheed company number for FDL-5 A unmanned model was
CL 639-1-167

4 small 500lbs rocket motors were used, for landing.

The nose cap materials included thoria, tungsten and tantalum.

The FDL-5 used high temperature resistant metals.

The vehicle also utilized densified cryogenic fuels, providing it with a higher Isp than standard LOX/LH2 fuel.
In the case of the Unmanned FDL-5 A from Lockheed, studies by Martin Marietta called for a Diboride VIII heat protection coating (56% ZrB2, (zirconium and bore), 14% SiC, (silica and carbone), and 30% C (carbone) by volume), "to be applied to the nose tip and leading edge components to the first 46 inches of the Air Force FDL-5 A Lifting body configuration".
The coating extended 4 inches along the side of the leading edges.

The use of diboride ceramics and components and metal attachment structures were defined. Plasma arc tests were conducted to ascertain the thermal stability, heat transfer characteristics, and thermal stress resistance of diboride ceramics.

"Full-scale diboride nose, skirt, and leading edge components were designed to replace existing water-cooled units on the Hypersonics Aerospace Test Structure (HATS)" (end of citation).

So here it confirms that actual hardware was build for the FDL-5 project.

This is from "Ceramic Nose Cap and Leading Edges for high Performance Weapon Systems."

Launch of the Unmanned version would have required an external booster, type unknown, either from under the wing of a B-52 motherplane, or using an ICBM. Umbilicals were present on the FDL-5 A.

"For the low-altitude reference trajectory, the proposed structure materials were: tungsten-thoria for the nose cap, coated tantalum for the leading edges, coated columbium for the lower surface, and Inconel for the upper surface. The leading edge must material must be extended approximately 4 inches beyond the leading-edge/side-panel tangency line, and portions of the forward upper surface must be fabricated from this material, such as coated tantalum."

34 years later, most of the story of FDL-5 MA is still classified, as are the other photos of that spacecraft which have not yet ever been shown to the public. The documents are still "need to know only", but are available to the industry and gov't. Getting the little information publicly available, and interpreting the data and correlating it to piece together this research was a work of 4 years. Analyzing and understanding how it was put together precisely required building the model, And finally, finding the dimensions took a few minutes... and I might say, I had it right under my nose for at least 3 years..

Text and model photos, Copyright: Stéphane Cochin & Stratosphere Models, March 2004.
Hosting permission for the text, photos and data granted only to Ninfinger.org, and Stratosphere Models website. Other permissions will require my personal agreement.
Permission to create links to this text and photos is gladly granted to anyone who wants to share the news about my research which lead to the creation of this new kit. But no permission to copy by any electronic or mechanical means, past, present or future, the text and photos, except in the framework of personal non-profit personal study. This does not allow however copying this text or photos into one's personal webpage.
Permission to reproduce pictures of the kit by the press, media, magazines, news websites and newspapers will be granted and encouraged, provided you first contact me via e-mail to ask for my permission. You can contact me at: stratospheremodels@yahoo.fr
These are the photos as of September 2003: